A nonvolatile semiconductor memory device uses the charge storage state in a charge storage layer to store information. There is a demand for increasing a program speed in this type of nonvolatile semiconductor memory device.
Since a conventional nonvolatile semiconductor memory device exhibits a low charge trapping efficiency in a charge storage layer, it is an impediment to increase the program speed. When the charge trapping efficiency is low, the time required for programming is increased, and there is a tendency for deterioration in memory cells due to the program operation.